I'm not at all a vet, just someone whose ferrets have had insulinoma, but
it's my understanding from what vets have told me, what I've read here, and
what I've read in the more novice-friendly veterinary books that pred should
be given 2x per day. I would speculate that the pred doesn't last in a
ferret's system more than 12 hours, so it's needed 2x per day, but I'm
guessing. I would go back to your vet and ask about this...